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unify.c
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unify.c
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/*************************************************************************
* *
* YAP Prolog *
* *
* Yap Prolog was developed at NCCUP - Universidade do Porto *
* *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997 *
* *
**************************************************************************
* *
* File: unify.c *
* Last rev: *
* mods: *
* comments: Unification and other auxiliary routines for absmi *
* *
*************************************************************************/
/** @defgroup Rational_Trees Rational Trees
@ingroup extensions
@{
Prolog unification is not a complete implementation. For efficiency
considerations, Prolog systems do not perform occur checks while
unifying terms. As an example, `X = a(X)` will not fail but instead
will create an infinite term of the form `a(a(a(a(a(...)))))`, or
<em>rational tree</em>.
Rational trees are now supported by default in YAP. In previous
versions, this was not the default and these terms could easily lead
to infinite computation. For example, `X = a(X), X = X` would
enter an infinite loop.
The `RATIONAL_TREES` flag improves support for these
terms. Internal primitives are now aware that these terms can exist, and
will not enter infinite loops. Hence, the previous unification will
succeed. Another example, `X = a(X), ground(X)` will succeed
instead of looping. Other affected built-ins include the term comparison
primitives, numbervars/3, copy_term/2, and the internal
data base routines. The support does not extend to Input/Output routines
or to assert/1 YAP does not allow directly reading
rational trees, and you need to use `write_depth/2` to avoid
entering an infinite cycle when trying to write an infinite term.
*/
#define IN_UNIFY_C 1
#define HAS_CACHE_REGS 1
#include "absmi.h"
int Yap_rational_tree_loop(CELL *, CELL *, CELL **, CELL **);
static int OCUnify_complex(CELL *, CELL *, CELL *);
static int OCUnify(register CELL, register CELL);
static Int p_ocunify( USES_REGS1 );
/* support for rational trees and unification with occur checking */
#define to_visit_base ((struct v_record *)AuxSp)
int
Yap_rational_tree_loop(CELL *pt0, CELL *pt0_end, CELL **to_visit, CELL **to_visit_max)
{
CELL ** base = to_visit;
rtree_loop:
while (pt0 < pt0_end) {
register CELL *ptd0;
register CELL d0;
ptd0 = ++pt0;
pt0 = ptd0;
d0 = *ptd0;
deref_head(d0, rtree_loop_unk);
rtree_loop_nvar:
{
if (d0 == TermFoundVar)
goto cufail;
if (IsPairTerm(d0)) {
to_visit -= 3;
if (to_visit < to_visit_max) {
to_visit = Yap_shift_visit(to_visit, &to_visit_max, &base);
}
to_visit[0] = pt0;
to_visit[1] = pt0_end;
to_visit[2] = (CELL *)*pt0;
*pt0 = TermFoundVar;
pt0_end = (pt0 = RepPair(d0) - 1) + 2;
continue;
}
if (IsApplTerm(d0)) {
register Functor f;
register CELL *ap2;
/* store the terms to visit */
ap2 = RepAppl(d0);
f = (Functor) (*ap2);
/* compare functors */
if (IsExtensionFunctor(f)) {
continue;
}
to_visit -= 3;
if (to_visit < to_visit_max) {
to_visit = Yap_shift_visit(to_visit, &to_visit_max, &base);
}
to_visit[0] = pt0;
to_visit[1] = pt0_end;
to_visit[2] = (CELL *)*pt0;
*pt0 = TermFoundVar;
d0 = ArityOfFunctor(f);
pt0 = ap2;
pt0_end = ap2 + d0;
continue;
}
continue;
}
derefa_body(d0, ptd0, rtree_loop_unk, rtree_loop_nvar);
}
/* Do we still have compound terms to visit */
if (to_visit < base) {
pt0 = to_visit[0];
pt0_end = to_visit[1];
*pt0 = (CELL)to_visit[2];
to_visit += 3;
goto rtree_loop;
}
return FALSE;
cufail:
/* we found an infinite term */
while (to_visit < (CELL **)base) {
CELL *pt0;
pt0 = to_visit[0];
*pt0 = (CELL)to_visit[2];
to_visit += 3;
}
return TRUE;
}
static inline int
rational_tree(Term d0) {
CACHE_REGS
CELL **to_visit_max = (CELL **)AuxBase, **to_visit = (CELL **)AuxSp;
if (IsPairTerm(d0)) {
CELL *pt0 = RepPair(d0);
return Yap_rational_tree_loop(pt0-1, pt0+1, to_visit, to_visit_max);
} else if (IsApplTerm(d0)) {
CELL *pt0 = RepAppl(d0);
Functor f = (Functor)(*pt0);
if (IsExtensionFunctor(f))
return FALSE;
return Yap_rational_tree_loop(pt0, pt0+ArityOfFunctor(f), to_visit, to_visit_max);
} else
return FALSE;
}
static int
OCUnify_complex(CELL *pt0, CELL *pt0_end, CELL *pt1)
{
CACHE_REGS
#ifdef THREADS
#undef Yap_REGS
register REGSTORE *regp = Yap_regp;
#define Yap_REGS (*regp)
#elif defined(SHADOW_REGS)
#if defined(B) || defined(TR)
register REGSTORE *regp = &Yap_REGS;
#define Yap_REGS (*regp)
#endif /* defined(B) || defined(TR) || defined(HB) */
#endif
#ifdef SHADOW_HB
register CELL *HBREG = HB;
#endif /* SHADOW_HB */
struct unif_record *unif = (struct unif_record *)AuxBase;
struct v_record *to_visit = (struct v_record *)AuxSp;
#define unif_base ((struct unif_record *)AuxBase)
loop:
while (pt0 < pt0_end) {
register CELL *ptd0 = pt0+1;
register CELL d0;
++pt1;
pt0 = ptd0;
d0 = *ptd0;
deref_head(d0, unify_comp_unk);
unify_comp_nvar:
{
register CELL *ptd1 = pt1;
register CELL d1 = *ptd1;
deref_head(d1, unify_comp_nvar_unk);
unify_comp_nvar_nvar:
if (d0 == d1) {
if (Yap_rational_tree_loop(pt0-1, pt0, (CELL **)to_visit, (CELL **)unif))
goto cufail;
continue;
}
if (IsPairTerm(d0)) {
if (!IsPairTerm(d1)) {
goto cufail;
}
/* now link the two structures so that no one else will */
/* come here */
/* store the terms to visit */
if (RATIONAL_TREES || pt0 < pt0_end) {
to_visit --;
#ifdef RATIONAL_TREES
unif++;
#endif
if ((void *)to_visit < (void *)unif) {
CELL **urec = (CELL **)unif;
to_visit = (struct v_record *)Yap_shift_visit((CELL **)to_visit, &urec, NULL);
unif = (struct unif_record *)urec;
}
to_visit->start0 = pt0;
to_visit->end0 = pt0_end;
to_visit->start1 = pt1;
#ifdef RATIONAL_TREES
unif[-1].old = *pt0;
unif[-1].ptr = pt0;
*pt0 = d1;
#endif
}
pt0_end = (pt0 = RepPair(d0) - 1) + 2;
pt1 = RepPair(d1) - 1;
continue;
}
if (IsApplTerm(d0)) {
register Functor f;
register CELL *ap2, *ap3;
if (!IsApplTerm(d1)) {
goto cufail;
}
/* store the terms to visit */
ap2 = RepAppl(d0);
ap3 = RepAppl(d1);
f = (Functor) (*ap2);
/* compare functors */
if (f != (Functor) *ap3)
goto cufail;
if (IsExtensionFunctor(f)) {
if (unify_extension(f, d0, ap2, d1))
continue;
goto cufail;
}
/* now link the two structures so that no one else will */
/* come here */
/* store the terms to visit */
if (RATIONAL_TREES || pt0 < pt0_end) {
to_visit --;
#ifdef RATIONAL_TREES
unif++;
#endif
if ((void *)to_visit < (void *)unif) {
CELL **urec = (CELL **)unif;
to_visit = (struct v_record *)Yap_shift_visit((CELL **)to_visit, &urec, NULL);
unif = (struct unif_record *)urec;
}
to_visit->start0 = pt0;
to_visit->end0 = pt0_end;
to_visit->start1 = pt1;
#ifdef RATIONAL_TREES
unif[-1].old = *pt0;
unif[-1].ptr = pt0;
*pt0 = d1;
#endif
}
d0 = ArityOfFunctor(f);
pt0 = ap2;
pt0_end = ap2 + d0;
pt1 = ap3;
continue;
}
goto cufail;
derefa_body(d1, ptd1, unify_comp_nvar_unk, unify_comp_nvar_nvar);
/* d1 and pt2 have the unbound value, whereas d0 is bound */
Bind_Global(ptd1, d0);
if (Yap_rational_tree_loop(ptd1-1, ptd1, (CELL **)to_visit, (CELL **)unif))
goto cufail;
continue;
}
derefa_body(d0, ptd0, unify_comp_unk, unify_comp_nvar);
/* first arg var */
{
register CELL d1;
register CELL *ptd1;
ptd1 = pt1;
d1 = ptd1[0];
/* pt2 is unbound */
deref_head(d1, unify_comp_var_unk);
unify_comp_var_nvar:
/* pt2 is unbound and d1 is bound */
Bind_Global(ptd0, d1);
if (Yap_rational_tree_loop(ptd0-1, ptd0, (CELL **)to_visit, (CELL **)unif))
goto cufail;
continue;
derefa_body(d1, ptd1, unify_comp_var_unk, unify_comp_var_nvar);
/* ptd0 and ptd1 are unbound */
UnifyGlobalCells(ptd0, ptd1);
}
}
/* Do we still have compound terms to visit */
if (to_visit < to_visit_base) {
pt0 = to_visit->start0;
pt0_end = to_visit->end0;
pt1 = to_visit->start1;
to_visit++;
goto loop;
}
#ifdef RATIONAL_TREES
/* restore bindigs */
while (unif-- != unif_base) {
CELL *pt0;
pt0 = unif->ptr;
*pt0 = unif->old;
}
#endif
return TRUE;
cufail:
#ifdef RATIONAL_TREES
/* restore bindigs */
while (unif-- != unif_base) {
CELL *pt0;
pt0 = unif->ptr;
*pt0 = unif->old;
}
#endif
return FALSE;
#ifdef THREADS
#undef Yap_REGS
#define Yap_REGS (*Yap_regp)
#elif defined(SHADOW_REGS)
#if defined(B) || defined(TR)
#undef Yap_REGS
#endif /* defined(B) || defined(TR) */
#endif
#undef unif_base
#undef to_visit_base
}
static int
OCUnify(register CELL d0, register CELL d1)
{
CACHE_REGS
register CELL *pt0, *pt1;
#if SHADOW_HB
register CELL *HBREG = HB;
#endif
deref_head(d0, oc_unify_unk);
oc_unify_nvar:
/* d0 is bound */
deref_head(d1, oc_unify_nvar_unk);
oc_unify_nvar_nvar:
if (d0 == d1) {
return (!rational_tree(d0));
}
/* both arguments are bound */
if (IsPairTerm(d0)) {
if (!IsPairTerm(d1)) {
return (FALSE);
}
pt0 = RepPair(d0);
pt1 = RepPair(d1);
return (OCUnify_complex(pt0 - 1, pt0 + 1, pt1 - 1));
}
else if (IsApplTerm(d0)) {
if (!IsApplTerm(d1))
return (FALSE);
pt0 = RepAppl(d0);
d0 = *pt0;
pt1 = RepAppl(d1);
d1 = *pt1;
if (d0 != d1) {
return (FALSE);
} else {
if (IsExtensionFunctor((Functor)d0)) {
switch(d0) {
case (CELL)FunctorDBRef:
return(pt0 == pt1);
case (CELL)FunctorLongInt:
return(pt0[1] == pt1[1]);
case (CELL)FunctorDouble:
return(FloatOfTerm(AbsAppl(pt0)) == FloatOfTerm(AbsAppl(pt1)));
case (CELL)FunctorString:
return(strcmp( (const char *)(pt0+2), (const char *)(pt1+2)) == 0);
#ifdef USE_GMP
case (CELL)FunctorBigInt:
return(Yap_gmp_tcmp_big_big(AbsAppl(pt0),AbsAppl(pt0)) == 0);
#endif /* USE_GMP */
default:
return(FALSE);
}
}
return (OCUnify_complex(pt0, pt0 + ArityOfFunctor((Functor) d0),
pt1));
}
} else {
return(FALSE);
}
deref_body(d1, pt1, oc_unify_nvar_unk, oc_unify_nvar_nvar);
/* d0 is bound and d1 is unbound */
YapBind(pt1, d0);
/* local variables cannot be in a term */
if (pt1 > HR && pt1 < LCL0)
return TRUE;
if (rational_tree(d0))
return(FALSE);
return (TRUE);
deref_body(d0, pt0, oc_unify_unk, oc_unify_nvar);
/* pt0 is unbound */
deref_head(d1, oc_unify_var_unk);
oc_unify_var_nvar:
/* pt0 is unbound and d1 is bound */
YapBind(pt0, d1);
/* local variables cannot be in a term */
if (pt0 > HR && pt0 < LCL0)
return TRUE;
if (rational_tree(d1))
return(FALSE);
return (TRUE);
deref_body(d1, pt1, oc_unify_var_unk, oc_unify_var_nvar);
/* d0 and pt1 are unbound */
UnifyCells(pt0, pt1);
return (TRUE);
return (TRUE);
}
static Int
p_ocunify( USES_REGS1 )
{
return(OCUnify(ARG1,ARG2));
}
static Int
p_cyclic( USES_REGS1 )
{
Term t = Deref(ARG1);
if (IsVarTerm(t))
return(FALSE);
return rational_tree(t);
}
int Yap_IsAcyclicTerm(Term t)
{
return !rational_tree(t);
}
static Int
p_acyclic( USES_REGS1 )
{
Term t = Deref(ARG1);
if (IsVarTerm(t))
return(TRUE);
return !rational_tree(t);
}
int
Yap_IUnify(register CELL d0, register CELL d1)
{
CACHE_REGS
#if THREADS
#undef Yap_REGS
register REGSTORE *regp = Yap_regp;
#define Yap_REGS (*regp)
#elif SHADOW_REGS
#if defined(B) || defined(TR)
register REGSTORE *regp = &Yap_REGS;
#define Yap_REGS (*regp)
#endif /* defined(B) || defined(TR) */
#endif
#if SHADOW_HB
register CELL *HBREG = HB;
#endif
register CELL *pt0, *pt1;
deref_head(d0, unify_unk);
unify_nvar:
/* d0 is bound */
deref_head(d1, unify_nvar_unk);
unify_nvar_nvar:
/* both arguments are bound */
if (d0 == d1)
return TRUE;
if (IsPairTerm(d0)) {
if (!IsPairTerm(d1)) {
return (FALSE);
}
pt0 = RepPair(d0);
pt1 = RepPair(d1);
return (IUnify_complex(pt0 - 1, pt0 + 1, pt1 - 1));
}
else if (IsApplTerm(d0)) {
pt0 = RepAppl(d0);
d0 = *pt0;
if (!IsApplTerm(d1))
return (FALSE);
pt1 = RepAppl(d1);
d1 = *pt1;
if (d0 != d1) {
return (FALSE);
} else {
if (IsExtensionFunctor((Functor)d0)) {
switch(d0) {
case (CELL)FunctorDBRef:
return(pt0 == pt1);
case (CELL)FunctorLongInt:
return(pt0[1] == pt1[1]);
case (CELL)FunctorString:
return(strcmp( (const char *)(pt0+2), (const char *)(pt1+2)) == 0);
case (CELL)FunctorDouble:
return(FloatOfTerm(AbsAppl(pt0)) == FloatOfTerm(AbsAppl(pt1)));
#ifdef USE_GMP
case (CELL)FunctorBigInt:
return(Yap_gmp_tcmp_big_big(AbsAppl(pt0),AbsAppl(pt0)) == 0);
#endif /* USE_GMP */
default:
return(FALSE);
}
}
return (IUnify_complex(pt0, pt0 + ArityOfFunctor((Functor) d0),
pt1));
}
} else {
return (FALSE);
}
deref_body(d1, pt1, unify_nvar_unk, unify_nvar_nvar);
/* d0 is bound and d1 is unbound */
YapBind(pt1, d0);
return (TRUE);
deref_body(d0, pt0, unify_unk, unify_nvar);
/* pt0 is unbound */
deref_head(d1, unify_var_unk);
unify_var_nvar:
/* pt0 is unbound and d1 is bound */
YapBind(pt0, d1);
return TRUE;
#if TRAILING_REQUIRES_BRANCH
unify_var_nvar_trail:
DO_TRAIL(pt0);
return TRUE;
#endif
deref_body(d1, pt1, unify_var_unk, unify_var_nvar);
/* d0 and pt1 are unbound */
UnifyCells(pt0, pt1);
return (TRUE);
#if THREADS
#undef Yap_REGS
#define Yap_REGS (*Yap_regp)
#elif SHADOW_REGS
#if defined(B) || defined(TR)
#undef Yap_REGS
#endif /* defined(B) || defined(TR) */
#endif
}
/**********************************************************************
* *
* Conversion from Label to Op *
* *
**********************************************************************/
#if USE_THREADED_CODE
/* mask a hash table that allows for fast reverse translation from
instruction address to corresponding opcode */
static void
InitReverseLookupOpcode(void)
{
op_entry *opeptr;
op_numbers i;
/* 2 K should be OK */
int hash_size_mask = OP_HASH_SIZE-1;
UInt sz = OP_HASH_SIZE*sizeof(struct opcode_tab_entry);
while (OP_RTABLE == NULL) {
if ((OP_RTABLE = (op_entry *)Yap_AllocCodeSpace(sz)) == NULL) {
if (!Yap_growheap(FALSE, sz, NULL)) {
Yap_Error(SYSTEM_ERROR_INTERNAL, TermNil,
"Couldn't obtain space for the reverse translation opcode table");
}
}
}
memset(OP_RTABLE, 0, sz);
opeptr = OP_RTABLE;
/* clear up table */
{
int j;
for (j=0; j<OP_HASH_SIZE; j++) {
opeptr[j].opc = 0;
opeptr[j].opnum = _Ystop;
}
}
opeptr = OP_RTABLE;
opeptr[rtable_hash_op(Yap_opcode(_Ystop),hash_size_mask)].opc
= Yap_opcode(_Ystop);
/* now place entries */
for (i = _std_top; i > _Ystop; i--) {
OPCODE opc = Yap_opcode(i);
int j = rtable_hash_op(opc,hash_size_mask);
while (opeptr[j].opc) {
if (++j > hash_size_mask)
j = 0;
}
/* clear entry, no conflict */
opeptr[j].opnum = i;
opeptr[j].opc = opc;
}
}
#endif
#define UnifyAndTrailGlobalCells(a, b) \
if((a) > (b)) { \
*(a) = (CELL)(b); \
DO_TRAIL((a), (CELL)(b)); \
} else if((a) < (b)){ \
*(b) = (CELL)(a); \
DO_TRAIL((b), (CELL)(a)); \
}
static int
unifiable_complex(CELL *pt0, CELL *pt0_end, CELL *pt1)
{
CACHE_REGS
#ifdef THREADS
#undef Yap_REGS
register REGSTORE *regp = Yap_regp;
#define Yap_REGS (*regp)
#elif defined(SHADOW_REGS)
#if defined(B) || defined(TR)
register REGSTORE *regp = &Yap_REGS;
#define Yap_REGS (*regp)
#endif /* defined(B) || defined(TR) || defined(HB) */
#endif
#ifdef SHADOW_HB
register CELL *HBREG = HB;
#endif /* SHADOW_HB */
struct unif_record *unif = (struct unif_record *)AuxBase;
struct v_record *to_visit = (struct v_record *)AuxSp;
#define unif_base ((struct unif_record *)AuxBase)
#define to_visit_base ((struct v_record *)AuxSp)
loop:
while (pt0 < pt0_end) {
register CELL *ptd0 = pt0+1;
register CELL d0;
++pt1;
pt0 = ptd0;
d0 = *ptd0;
deref_head(d0, unifiable_comp_unk);
unifiable_comp_nvar:
{
register CELL *ptd1 = pt1;
register CELL d1 = *ptd1;
deref_head(d1, unifiable_comp_nvar_unk);
unifiable_comp_nvar_nvar:
if (d0 == d1)
continue;
if (IsPairTerm(d0)) {
if (!IsPairTerm(d1)) {
goto cufail;
}
/* now link the two structures so that no one else will */
/* come here */
/* store the terms to visit */
if (RATIONAL_TREES || pt0 < pt0_end) {
to_visit --;
#ifdef RATIONAL_TREES
unif++;
#endif
if ((void *)to_visit < (void *)unif) {
CELL **urec = (CELL **)unif;
to_visit = (struct v_record *)Yap_shift_visit((CELL **)to_visit, &urec, NULL);
unif = (struct unif_record *)urec;
}
to_visit->start0 = pt0;
to_visit->end0 = pt0_end;
to_visit->start1 = pt1;
#ifdef RATIONAL_TREES
unif[-1].old = *pt0;
unif[-1].ptr = pt0;
*pt0 = d1;
#endif
}
pt0_end = (pt0 = RepPair(d0) - 1) + 2;
pt1 = RepPair(d1) - 1;
continue;
}
if (IsApplTerm(d0)) {
register Functor f;
register CELL *ap2, *ap3;
if (!IsApplTerm(d1)) {
goto cufail;
}
/* store the terms to visit */
ap2 = RepAppl(d0);
ap3 = RepAppl(d1);
f = (Functor) (*ap2);
/* compare functors */
if (f != (Functor) *ap3)
goto cufail;
if (IsExtensionFunctor(f)) {
if (unify_extension(f, d0, ap2, d1))
continue;
goto cufail;
}
/* now link the two structures so that no one else will */
/* come here */
/* store the terms to visit */
if (RATIONAL_TREES || pt0 < pt0_end) {
to_visit --;
#ifdef RATIONAL_TREES
unif++;
#endif
if ((void *)to_visit < (void *)unif) {
CELL **urec = (CELL **)unif;
to_visit = (struct v_record *)Yap_shift_visit((CELL **)to_visit, &urec, NULL);
unif = (struct unif_record *)urec;
}
to_visit->start0 = pt0;
to_visit->end0 = pt0_end;
to_visit->start1 = pt1;
#ifdef RATIONAL_TREES
unif[-1].old = *pt0;
unif[-1].ptr = pt0;
*pt0 = d1;
#endif
}
d0 = ArityOfFunctor(f);
pt0 = ap2;
pt0_end = ap2 + d0;
pt1 = ap3;
continue;
}
goto cufail;
derefa_body(d1, ptd1, unifiable_comp_nvar_unk, unifiable_comp_nvar_nvar);
/* d1 and pt2 have the unbound value, whereas d0 is bound */
*(ptd1) = d0;
DO_TRAIL(ptd1, d0);
continue;
}
derefa_body(d0, ptd0, unifiable_comp_unk, unifiable_comp_nvar);
/* first arg var */
{
register CELL d1;
register CELL *ptd1;
ptd1 = pt1;
d1 = ptd1[0];
/* pt2 is unbound */
deref_head(d1, unifiable_comp_var_unk);
unifiable_comp_var_nvar:
/* pt2 is unbound and d1 is bound */
*ptd0 = d1;
DO_TRAIL(ptd0, d1);
continue;
derefa_body(d1, ptd1, unifiable_comp_var_unk, unifiable_comp_var_nvar);
/* ptd0 and ptd1 are unbound */
UnifyAndTrailGlobalCells(ptd0, ptd1);
}
}
/* Do we still have compound terms to visit */
if (to_visit < to_visit_base) {
pt0 = to_visit->start0;
pt0_end = to_visit->end0;
pt1 = to_visit->start1;
to_visit++;
goto loop;
}
#ifdef RATIONAL_TREES
/* restore bindigs */
while (unif-- != unif_base) {
CELL *pt0;
pt0 = unif->ptr;
*pt0 = unif->old;
}
#endif
return TRUE;
cufail:
#ifdef RATIONAL_TREES
/* restore bindigs */
while (unif-- != unif_base) {
CELL *pt0;
pt0 = unif->ptr;
*pt0 = unif->old;
}
#endif
return FALSE;
#ifdef THREADS
#undef Yap_REGS
#define Yap_REGS (*Yap_regp)
#elif defined(SHADOW_REGS)
#if defined(B) || defined(TR)
#undef Yap_REGS
#endif /* defined(B) || defined(TR) */
#endif
}
/* don't pollute name space */
#undef to_visit_base
#undef unif_base
static int
unifiable(CELL d0, CELL d1)
{
CACHE_REGS
#if THREADS
#undef Yap_REGS
register REGSTORE *regp = Yap_regp;
#define Yap_REGS (*regp)
#elif SHADOW_REGS
#if defined(B) || defined(TR)
register REGSTORE *regp = &Yap_REGS;
#define Yap_REGS (*regp)
#endif /* defined(B) || defined(TR) */
#endif
#if SHADOW_HB
register CELL *HBREG = HB;
#endif
register CELL *pt0, *pt1;
deref_head(d0, unifiable_unk);
unifiable_nvar:
/* d0 is bound */
deref_head(d1, unifiable_nvar_unk);
unifiable_nvar_nvar:
/* both arguments are bound */
if (d0 == d1)
return TRUE;
if (IsPairTerm(d0)) {
if (!IsPairTerm(d1)) {
return (FALSE);
}
pt0 = RepPair(d0);
pt1 = RepPair(d1);
return (unifiable_complex(pt0 - 1, pt0 + 1, pt1 - 1));
}
else if (IsApplTerm(d0)) {
pt0 = RepAppl(d0);
d0 = *pt0;
if (!IsApplTerm(d1))
return (FALSE);
pt1 = RepAppl(d1);
d1 = *pt1;
if (d0 != d1) {
return (FALSE);
} else {
if (IsExtensionFunctor((Functor)d0)) {
switch(d0) {
case (CELL)FunctorDBRef:
return(pt0 == pt1);
case (CELL)FunctorLongInt:
return(pt0[1] == pt1[1]);
case (CELL)FunctorString:
return(strcmp( (const char *)(pt0+2), (const char *)(pt1+2)) == 0);
case (CELL)FunctorDouble:
return(FloatOfTerm(AbsAppl(pt0)) == FloatOfTerm(AbsAppl(pt1)));
#ifdef USE_GMP
case (CELL)FunctorBigInt:
return(Yap_gmp_tcmp_big_big(AbsAppl(pt0),AbsAppl(pt0)) == 0);
#endif /* USE_GMP */
default:
return(FALSE);
}
}
return (unifiable_complex(pt0, pt0 + ArityOfFunctor((Functor) d0),
pt1));
}
} else {
return (FALSE);
}
deref_body(d1, pt1, unifiable_nvar_unk, unifiable_nvar_nvar);
/* d0 is bound and d1 is unbound */
*(pt1) = d0;
DO_TRAIL(pt1, d0);
return (TRUE);
deref_body(d0, pt0, unifiable_unk, unifiable_nvar);
/* pt0 is unbound */
deref_head(d1, unifiable_var_unk);
unifiable_var_nvar:
/* pt0 is unbound and d1 is bound */
*pt0 = d1;
DO_TRAIL(pt0, d1);
return TRUE;
deref_body(d1, pt1, unifiable_var_unk, unifiable_var_nvar);
/* d0 and pt1 are unbound */
UnifyAndTrailCells(pt0, pt1);
return (TRUE);
#if THREADS
#undef Yap_REGS
#define Yap_REGS (*Yap_regp)
#elif SHADOW_REGS
#if defined(B) || defined(TR)
#undef Yap_REGS
#endif /* defined(B) || defined(TR) */
#endif
}
static Int
p_unifiable( USES_REGS1 )
{
tr_fr_ptr trp, trp0 = TR;
Term tf = TermNil;
if (!unifiable(ARG1,ARG2)) {
return FALSE;
}
trp = TR;
while (trp != trp0) {
Term t[2];
--trp;
t[0] = TrailTerm(trp);
t[1] = *(CELL *)t[0];
tf = MkPairTerm(Yap_MkApplTerm(FunctorEq,2,t),tf);
RESET_VARIABLE(t[0]);
}
return Yap_unify(ARG3, tf);
}
int
Yap_Unifiable( Term d0, Term d1 )
{
CACHE_REGS
tr_fr_ptr trp, trp0 = TR;
if (!unifiable(d0,d1)) {
return FALSE;
}
trp = TR;
while (trp != trp0) {
Term t;
--trp;
t = TrailTerm(trp);
RESET_VARIABLE(t);
}
return TRUE;
}
void
Yap_InitUnify(void)
{
CACHE_REGS
Term cm = CurrentModule;
Yap_InitCPred("unify_with_occurs_check", 2, p_ocunify, SafePredFlag);
/** @pred unify_with_occurs_check(?T1,?T2) is iso
Obtain the most general unifier of terms _T1_ and _T2_, if there